1.4.5

Surds

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Surds

Surds are expressions like 3√6. They contain irrational numbers. These are numbers which can't be expressed as normal numbers or as a fraction. The rules for surds are:

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Simplifying Surds

If the number inside the root has a factor which is a square number the surd can be simplified.

Rationalising the Denominator

It is often easier to work with surds when there are no square roots on the bottom of a fraction. Removing surds from the bottom of a fraction is called ‘rationalising the denominator’.

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Advanced example

  • To rationalise a denominator of the form a ± √b multiply by the denominator but with the sign in front of the root changed.
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Exact form

  • Leaving an answer in exact form means leaving any fractions, surds and constants like in the expression rather than giving the answer as a decimal.

Jump to other topics

1Numbers

2Equations, Formulae & Identities

3Sequences, Functions & Graphs

4Geometry

5Vectors & Transformation Geometry

6Statistics & Probability

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